Allow creating hedged ECDSA signatures?

[twiss]

Similarly to #424, we may want to allow generating hedged ECDSA signatures, as per draft-irtf-cfrg-det-sigs-with-noise.

Unlike in EdDSA, there should be essentially no observable difference to doing so, since ECDSA signatures are already randomized today.

[ChALkeR]

Per nodejs/node#62252 (comment), implementations using OpenSSL are already effectively hedged, as they not just do direct CSRPNG->nonce, but mixin input and the key during nonce generation:
https://github.com/openssl/openssl/blob/67b5686b4419b4cb8caa502711c41815f5279751/crypto/bn/bn_rand.c#L285-L395

Also, the difference is unobservable from the API surface
Hedged signatures are already "allowed" in that sense

And there hardly needs to be an API that switches the underlying impl between e.g. what OpenSSL is currently doing and draft-irtf-cfrg-det-sigs-with-noise.
So if "allow" means introducing new APIs to switch between something random-looking/hedged then I don't think that's needed?

If that (what OpenSSL is doing) is the status in all platforms, then the spec could be just updated to prohibit CSRPNG->nonce specifically / urge the implementers to use a nonce generation method that survives a broken CSRPNG.

[twiss]

So if "allow" means introducing new APIs to switch between something random-looking/hedged then I don't think that's needed?

No, that's indeed not what I meant. The only thing that needs to be done is to change the reference for ECDSA from RFC6090 to "RFC6090 or <whatever RFC draft-irtf-cfrg-det-sigs-with-noise ends up being>".

If that (what OpenSSL is doing) is the status in all platforms, then the spec could be just updated to prohibit CSRPNG->nonce specifically / urge the implementers to use a nonce generation method that survives a broken CSRPNG.

I'm not sure what other implementations are doing but I somewhat doubt everyone implemented this draft; perhaps @Frosne knows for NSS, for example?

I'm also not sure we need to mandate it; IMHO it also depends a bit on the platform and the quality of the source of randomness there whether this is needed.